The use of welding automated processes in many industrial applications is increasingly growing. It is common practice for such technology to feed welding wires, sometimes at significantly high speed, from large bulk containers holding up to 1000 kgs of welding consumable, from the container to the wire feeder and subsequently from the wire feeder to the welding torch.
There are some general technical problems involved when welding wire is being fed over large distances. One issue is attrition which causes the welding wire to be fed intermittently and inconsistently, with consequent spatter and in most extreme cases, torch tip burn backs. Another issue is wire surface contamination. When a large quantity of welding wire is being fed through a liner, the drawing residues and lubricant which are normally present on the wire surface as a consequence of the wire drawing process, accumulate in the liner. Further, it must be ensured that there is no excessive wire deformation and cast bending which would result in the wire being fed deformed to the welding torch, with consequent unreliable weld placements. Finally, wire surface scratching must be prevented, as otherwise the copper coating would be scraped off the wire surface which would result in inconsistent bad electrical contact at the torch tip.
There are some welding wire guides which aim at solving these issues. One example can be found in FR 2 888 825 A1 which discloses a welding wire guide which consists of two guiding bodies placed in an alternating pattern. In a first guiding body, a first set of rolling elements is arranged which guide the welding wire in a first direction. In the second guiding body, a second set of rolling elements is provided which guide the welding wire in a second direction. It is only the combination of a first and a second guiding body which defines a complete guiding channel for the welding wire. As the first set of rolling elements is spaced from the second set of rolling elements, the welding wire can touch the guiding bodies when the guiding liner is curved, resulting in increased friction and wear.
WO 2009/143917 A1 discloses a welding wire liner which consists of a plurality of liner bodies connected to each other by means of a pivot connection. Each liner body comprises a set of rolling elements which guide the wire without friction.
EP 1 974 846 A2 discloses a welding wire liner which consists of a plurality of liner bodies connected to each other by means of a ball joint. This allows the bodies to swivel in any direction with respect to the previous body. Further, the bodies can be rotated with respect to each other, which allows using the liner for feeding the welding wire to a welding torch. In view of the particular configuration of the joints between adjacent liner bodies, the ability of withstanding torsional loads has proven to be limited. Modern multiple axis welding robots move in all directions and rotate the welding torch in some cases more than 360° and must be capable of doing so without any restriction. This movement results in tension being built up, caused by the swift and sharp movements in all directions which eventually causes the wire guiding liner assemblies to snap and break apart. If the wire guiding liner is tensioned by the robot movements and cannot adequately and quickly stretch out to follow and match the robot arm rapid movements, it represents an obstacle to the continuous and correct robot performance and in most cases, when damaged, it requires the welding operator to either repair or replace it, with unwanted costly stops and losses of production.
Our earlier patent application U.S. Ser. No. 12/618,250 addresses the issue of torsional loads by using swivel connections at discrete intervals along the liner. These swivel connections allow to discharge any tension which might have resulted from the movements of the welding torch to which the liner is fitted. However, each swivel connection forms an interruption of the guiding liner.
The object of the invention is to provide a welding wire guiding liner which fulfills the requirements regarding a reliable, smooth and low-friction guiding of the welding wire, and in addition allows rotational movements of a welding torch without creating excessive torsional loads in the liner.